Scanning calorimetry is being used as a technique for studying erythrocyte structure in relation to certain functions. The membrane undergoes four thermal transitions over the temperature range from 40 degrees to 75 degrees C. Information is now available concerning the particular membrane components which participate in each of these transitions. One of these transitions, the C transition, is shifted upwards by ca. 10 degrees C. when the membrane is interacted with micromolar amounts of specific inhibitors of anion transport, such DIDS. This suggests that the region of the membrane participating in this transition may also be involved in anion transport. Transport studies using radiolabelled sulfate ion confirm that this is the case. A combination of studies involving both proteases and phospholipases suggests that the 'C region' of the membrane contains the transmembrane portion of band 3 as well as phospholipids.